The incidental finding of a pituitary microadenoma (less than 10 mm in size) is not uncommon. Studies have suggested a 10 percent prevalence of pituitary microadenomas in the general population. Current recommendations for the evaluation of such an incidental finding are controversial. Some experts suggest extensive laboratory evaluation to determine levels of prolactin, growth hormone, adrenocorticotropic hormone (ACTH), thyroid-stimulating hormone, luteinizing hormone and follicle-stimulating hormone. Serial magnetic resonance images (MRI) may also be recommended to determine whether a change in the lesion has occurred. King and associates studied the cost effectiveness of four management strategies for incidentally discovered pituitary micro-adenomas.

The authors addressed the following four questions: (1) Does an incidental pituitary microadenoma put the patient at increased risk for an adverse outcome? (2) Can patients with treatable syndromes be accurately identified? (3) Is the treatment of these syndromes more effective in presymptomatic patients? (4) Do the beneficial effects of presymptomatic detection and treatment justify the costs incurred?

The following management strategies were assessed: (1) expectant management, with further testing performed only if endocrinologic or neurologic symptoms such as amenorrhea, galactorrhea or visual field problems develop; (2) prolactin screening, with hyperprolactinemia confirmed by a repeat test and treated with bromocriptine; (3) an endocrinologic screening panel that includes determination of prolactin, somatomedin C (insulin-like growth factor) and cortisol levels after administration of 1 mg of dexamethasone; and (4) follow-up of MRI scans. The model included issues such as the expected natural history of an incidental asymptomatic pituitary microadenoma, test characteristics, outcomes of pharmacologic and surgical interventions, quality of life, and costs of testing and treatment.

Determination of the prolactin level was found to be the most cost-effective management strategy for patients with asymptomatic, incidental pituitary microadenomas. An endocrine screening panel and follow-up MRI provided slightly greater quality-adjusted survival than expectant management, although the cost increased substantially.

The authors conclude that, while this study does not resolve the debate about conservative versus aggressive management of these lesions, it does provide evidence for a reasonable approach to patients with asymptomatic pituitary microadenomas. They note that the low prevalence of other endocrinopathies in patients with incidental pituitary microadenomas suggests that further evaluation of patients with normal prolactin levels confers little benefit and is not cost effective. Follow-up with MRI scanning provides no better clinical results than hormone screening.